The latest corruption scandal involving former key aides to ousted President Park Geun-hye should shed fresh light on the problems of the government’s audit-free “special activity accounts.”

It is not the first time that the accounts, intended to finance confidential government work, such as intelligence gathering and covert investigations, have been abused by corrupt officials, but the latest case is truly outrageous.

This time, the key players are the National Intelligence Service and former close aides to Park, who was impeached and put into jail over a massive corruption and influence-peddling scandal.

Prosecutors investigating past irregularities involving the NIS obtained testimony that a trio of former Park aides received money regularly from the spy agency’s special activity account.

In the first year of the Park presidency in 2013, each of the three -- Ahn Bong-geun, Lee Jae-man and Jeong Ho-seong -- received about 50 million ($45,000) each month, and it increased to 100 million won later. Altogether, the three are suspected of having taken a total of about 4 billion won until last year.

The three -- now all in custody -- are known as the “doorknob trio” because they were Park’s closest aides and were often said to hold the door to Park’s office open or closed.

What’s hardly surprising is that the three are not the only ones suspected of taking the audit-free money from the NIS. Prosecutors said former Culture Minister Cho Yoon-sun allegedly received money regularly from the NIS while she was the senior presidential secretary for political affairs under the Park administration. Her predecessor Hyun Ki-hwan and other lower-level Cheong Wa Dae officials were handed NIS money too.

Prosecutors said Cheong Wa Dae even used 500 million won of the NIS fund to conduct its own public opinion surveys regarding the parliamentary elections in April last year.

In other words, the money in the special activity account of the intelligence agency was up for grabs simply because it was free from audit. A bigger problem is that the latest case may be only the tip of the iceberg.

The NIS accounts for more than a half of the total special activity expenses in government -- 493 billion won of the 890 billion won in this year’s state budget. The NIS is now facing a massive investigation over its illegal intervention in domestic politics during the Park administration, and it is not hard to suspect that it used its special activity account fund to finance its illegal activities.

More troubling is that the NIS is not the only government agency that abuses its confidential account. For instance, Hong Joon-pyo, leader of the main opposition Liberty Korea Party, said that he “took home” part of the money he received from the National Assembly special activity account when he was the floor leader of the then ruling party in 2008.

Last year, public uproar erupted when senior prosecutors were found to have handed out cash envelopes -- carrying money from the special activity account of the state prosecution -- to their juniors at a dinner gathering.

These things indicate that the tradition of arbitrarily using the money in the account is deep-rooted and rampant in government offices. In fact, a former senior NIS official told investigators that NIS officials have made regular visits to senior presidential officials to provide secret money for decades.

So the Liberty Korea Party’s demand that the prosecution expand the probe into the past governments, including those of the liberal presidents Kim Dae-jung and Roh Moo-hyun, President Moon Jae-in’s former boss and political mentor, is not totally groundless.

Yet, what’s urgent is getting to the bottom of the case of the trio, all of whom are suspected of using the NIS money to buy apartments in expensive parts of Seoul. Lee Jae-man also testified that he got the NIS money under Park’s orders, which raise the need to verify whether she used any of it.

It is needless to say that the case should reawaken political and public attention to the need to reform the special activity account in a way to increase its transparency and accountability. The National Assembly should lead that effort.